The present invention relates generally to pressurized fluid systems and more particularly, but not by way of limitation, to a pressure relief system which uses a clutch mechanism to isolate a pressure response assembly from forces associated with a valve assembly used to provide a bypass or shutdown path.
Pressurized fluid systems are typically provided with pressure relief capabilities to prevent the possibility of injury to humans and damage to equipment in the event of an overpressure situation. Such pressure relief systems typically use a pressure responsive member which mechanically fails when subjected to a large increase in fluidic pressure.
A particularly advantageous pressure relief system uses a buckling pin arrangement such as taught by U.S. Pat. No. 4,724,857 issued to Taylor. In such a system, the pin is placed under compressive load along an axial length of the pin by the pressure of the fluid. A sufficient increase in fluid pressure above a nominal operational level causes the pin to buckle, or collapse, allowing a plunger or other mechanism to move to a position where a bypass path can be established to direct the fluid to reduce the pressure to a safe operational level.
A valve can be advantageously configured to open (or close) in response to the collapse of a buckling pin, such as disclosed in copending U.S. patent application Ser. No. 10/020,611 filed by Taylor. Such a system uses a rotary actuator assembly with a rack and pinion arrangement. Lateral movement of the rack in response to a collapse of the pin induces rotation of the pinion. The pinion is coupled to the bypass valve to induce the desired rotary motion to open or close the valve.
While operable, under certain circumstances system forces can undesirably affect the set point at which the pressure responsive member begins to fail. For example, friction forces and fluidic pressure can tend to offset the compressive load upon a buckling pin if the pin actuation and the valve are directly coupled.
There is therefore a continued need for improvements in the art to increase the accuracy and repeatability of pressure relief systems, and it is to such improvements that the present invention is directed.
A pressure relief system is provided to detect an overpressure situation in a pressurized fluid.
In accordance with preferred embodiments, a pressure response assembly is provided with a pressure responsive member such as a buckling pin which is configured to mechanically fail when a predetermined force is applied to the member. An actuator assembly is coupled to the pressure response assembly and includes a housing in which a slidable piston is disposed.
The piston applies a compressive force upon the member in response to a pressure of pressurized fluid introduced into the housing. Preferably, a pinion is mounted to a first shaft adjacent the piston and engages a rack of the piston. When the pressure of the pressurized fluid reaches a sufficient level to induce mechanical failure of the member, the piston slides past and engages the pinion. Thus, movement of the piston collapses the member to a final failed condition and at the same time induces rotation in the first shaft.
A bypass valve assembly is provided with a second shaft. The valve assembly establishes an overpressure path for the pressurized fluid when the second shaft is rotated by a selected amount (such as a quarter-turn). The overpressure path can comprise a bypass path (redirection of flow) or a shutdown path (interruption of flow).
A clutch mechanism is provided between the first and second shafts. The clutch mechanism decouples the first and second shafts during steady state operation (i.e., prior to mechanical failure of the member) and during initial stages of mechanical failure of the member. The clutch mechanism subsequently couples the first and second shafts during remaining stages of mechanical failure of the member so that continued rotation of the first shaft results in rotation of the second shaft and establishment of the overpressure path for the fluid by the valve assembly. In this way, forces associated with the valve assembly are isolated from the actuator assembly prior to and during the initial stages of mechanical failure, allowing the set point at which mechanical failure of the member begins to be accurately controlled.
These and various other features and advantages which characterize the claimed invention will become apparent upon reading the following detailed description and upon reviewing the associated drawings.